Thrombocytopenic purpura and chickenpox.

Examination of the bone marrow in thrombocytopenic purpura shows two main patterns: the megakaryocytes are either deficient or else present in normal or even increased numbers. The former group results from depression of the marrow as by poisoning or mechanical displacement of the cells themselves by foreign tissue in leukaemia, infiltration with malignant cells, replacement with bone or fibrous tissue and other similar conditions. The group with a relatively normal appearance has been found to include cases due to the presence of antiplatelet bodies in the serum, to hypersplenism, to specific allergic responses to certain drugs such as 'sedormid' and 'quinidine' and others which seem to follow sufficiently closely on an infection for it to play some part in producing the condition. The following three patients developed purpura after chickenpox, although the third also had a large haemangioma, a condition itself incriminated in the past in the pathogenesis of tlrombocytopenic purpura.